[graboid] Change the event searching logic.

[rthoth]

I was thinking here. Graboid now uses when the events happened as a guide to coordinate its work. Maybe it could be better to use when the events were recorded to coordinate its timeline.

For instance. Imagine that we have an event that took place yesterday, but Graboid managed its timeline to say "Okay, I'm already know what happened yesterday", but the event will be recorded tomorrow.